1. Field of the Invention
The present invention relates to methods of computerized numerical control of machine tools, and more particularly to a method of controlling a tool to move in an arbitrary plane.
2. Description of the Prior Art
Machine tools and similar apparatus may be controlled by computerized numerical controllers (CNC). In the prior art, CNCs operate by controlling a tool movement in a series of straight lines in space and in circular arcs in a plane. The CNC is directed by a computer program and a plane of operation is then selected by the computer programmer. In prior art systems, the plane has generally been limited to one of the "principal planes". That is, by xy, zx, and yz planes in a three dimensional rectangular coordinate system.
The EIA standard RS-274 program language includes constructs or "g codes" for selecting the principal planes. The plane selection is used in the CNC to determine the plane in which circular arcs and other planar curves are to be produced. Also, the plane in which cutter radius compensation (CRC) is to be applied is so selected, and the programmer will assume a certain size cutter. If a resharpened cutter is used, adjustments to the control are required and knowledge of a plane in which to apply CRC is necessary.
Plane selection is also necessary in determining the meaning of statements such as "the tool is to the left of the part it is cutting" since the data always assumes the point of reference is that of a person positioned within the CRC plane looking in the direction of the relative motion of the tool with respect to the part being cut.
Through the use of computer graphics, it is now possible for a CNC to display three dimensional images of the path along which a tool is being moved. Also, improvements in machine tool technology have produced axis configurations that make it possible to perform operations in an arbitrary plane that were earlier possible only in a principal plane. Thus, a method and system is required to provide cutter compensation and circular arc generation in an arbitrary plane. Preferably, programming should utilize RS-274 and be as similar as possible to that used in principal plane operations.